In 3GPP (3rd Generation Partnership Project) which is a standardization project, there have been examined an OFDM (Orthogonal Frequency-Division Multiplexing) communication system, and Evolved Universal Terrestrial Radio Access (hereinafter referred to as EUTRA) in which high-speed communication has been achieved by employing flexible scheduling of a predetermined frequency/time unit called a resource block and furthermore, examination of Advanced EUTRA (also referred to as LTE-Advanced) which is the evolved type of EUTRA has been advanced.
In Advanced EUTRA, carrier aggregation has been proposed as a technology which can perform higher-speed data transmission, while maintaining compatibility with EUTRA. Carrier aggregation is a technology which improves a data rate by respectively receiving data of transmission apparatus transmitted in a plurality of different frequency bands (also referred to as carrier frequencies or component carriers) in reception apparatuses corresponding to the different frequency bands. It should be noted that although hereinafter, a reception apparatus in downlink transmission is described as a mobile station apparatus, and a transmission apparatus in downlink transmission is described as a base station apparatus, while a reception apparatus in uplink transmission is described as the mobile station apparatus, and a transmission apparatus in uplink transmission is described as the mobile station apparatus, there is no need to limit the range of application of the present invention, to these apparatuses.
A mobile station apparatus of EUTRA determines whether or not a base station apparatus currently wirelessly-connected to the mobile station apparatus is appropriate as a communication destination by detecting a radio link problem in a higher layer. The radio link problem is the problem (a physical layer problem in a physical layer, or a random access problem in a data link layer) generated in a lower layer (the physical layer and the data link layer). The physical layer problem is detected by an RRC (Radio Resource Control) based on notification of downlink out-of-sync and notification of downlink in-sync which are comparison results of a reception quality of a transmission signal from the base station apparatus, and a threshold value in a physical layer.
In addition, the random access problem is detected by an MAC (Medium Access Control) of the data link layer, and the MAC notifies the RRC of the random access problem when the number of preamble transmission reaches the maximum number of transmission. The MAC mainly performs management of random access transmission, management of an uplink transmission timing gap, management of a buffer state, etc. The RRC mainly performs management of a state of the lower layer, management of radio resource control, mobility control, etc. In addition, the RRC detects a radio link failure indicating that an error has occurred in radio connection with the base station apparatus based on the radio link problem, which has been detected or notification of which has been provided.
It should be noted that a third generation base station apparatus specified by 3GPP is referred to as a node B (NodeB), and that abase station apparatus in EUTRA and Advanced EUTRA is referred to as an e-node B (eNodeB). The base station apparatus manages a cell which is an area where the mobile station apparatus can communicate with the base station apparatus, and the cell is also referred to as a femto cell, a pico cell, or a nano cell in accordance with a size of the area where the base station apparatus can communicate with the mobile station apparatus. In addition, when the base station apparatus can communicate with a certain mobile station apparatus, a cell of the base station apparatus is a serving cell of the mobile station apparatus, and a cell of other base station apparatuses or of a different frequency is referred to as a neighboring cell.